Lung disease is the third-leading cause of death in the United States, with more than 400,000 deaths annually (Longmire T A, et al. 2012. Cell Stem Cell 10(4):398-411, Petersen T H, et al. 2011. Material today 14(5):196-201). Lung transplantation is a possible treatment for people who have end-stage lung disease. Lung transplantation is limited by the low availability of donor lungs. Moreover, surgical, medical and immunological complications cause considerable morbidity and mortality in this population. As a result, many patients die each year while on a waiting list or because of transplant complications (Longmire T A, et al. 2012. Cell Stem Cell 10(4):398-411, Nichols J E, et al. 2012. J Cell Biochem 113(7):2185-2192, McCurry K R, et al. 2009. Am J Transplant 9(Part 2):942-958).
Transplantation of adult lung stem and progenitor cells or alveolar cells, isolated from human lung, is emerging as an alternative to whole organ transplantation (Wang D, et al. 2007. Proc Natl Acad Sci USA. 104(11):4449-4454). However, this approach is also limited by the scarcity of human epithelial cells, and the difficulties of expanding these cells in vitro. Moreover, the successful engraftment of such cells in vivo in injured lungs has not yet been demonstrated (Wang D, et al. 2007. Proc Natl Acad Sci USA. 104(11):4449-4454, Tesei A, et al. 2009. Cell Prolif 42(3):298-308, Fujino N, et al. 2012. Am J Respir Cell Mol Biol 46(4):422-430).
One potential future treatment for severe lung disease is transplantation with engineered lungs that are capable of gas exchange. To avoid immunological rejection, such engineered lungs should be created using individual-specific (autologous) lung and airway cells (Nichols J E, et al. 2012. J Cell Biochem 113(7):2185-2192, Petersen T H, et al. 2010. Science 329(5991):538-541, Badylak S F, et al. 2012. Lancet 379(9819):943-952). Therefore, a significant emphasis is being placed on identifying a reliable source of functional lung epithelial cells to be used in lung-related therapies (Petersen T H, et al. 2011. Material today 14(5):196-201, Kotton D N, et al. 2012. Am J Respir Crit Care Med 185(12):1255-1260).
Induced pluripotent stem (iPS) cells are the product of adult somatic cell reprogramming to an embryonic-like state by inducing a “forced” expression of specific pluripotent genes (Takahashi K, et al. 2007. Cell 131(5):861-872, Yu J, et al. 2007. Science 318(5858):1917-1920). It is postulated that the use of human iPS cells may be the most effective strategy to develop respiratory epithelial cells that may be valuable in lung-related cell therapies and tissue engineering (Nishikawa S, et al. 2008. Nat Rev Mol Cell Biol 9(9):725-729, Green M D, et al. 2011. Nat Biotechnol 29(3):267-272, Mou H, et al. 2012. Cell Stem Cell 10(4):385-397). Given that iPS cells can be derived from the patient to be treated, they could provide a cell source that is genetically identical to the patient, allowing tissue generated from these cells to avoid immune rejection (Badylak S F, et al. 2012. Lancet 379(9819):943-952, Yu J, et al. 2007. Science 318(5858):1917-1920).
The differentiation of human embryonic stem and iPS cells (hESCs and iPSCs, respectively) into pulmonary epithelium has been challenging. Several research groups have reported the successful differentiation toward a range of pulmonary epithelial cell types, including both alveolar type II cells (AETII cells) and other airway epithelium, using a variety of protocols (Longmire T A, et al. 2012. Cell Stem Cell 10(4):398-411, Wang D, et al. 2007. Proc Natl Acad Sci USA. 104(11):4449-4454, Green M D, et al. 2011. Nat Biotechnol 29(3):267-272, Mou H, et al. 2012. Cell Stem Cell 10(4):385-397, Van Haute L, et al. 2009. Respir Res 10:105, Ali N N, et al. 2002. Tissue Eng 8(4):541-550, Rippon H J, et al. 2006. Stem Cells 24(5):1389-1398, Samadikuchaksaraei A, et al. 2006. Tissue Eng 12(4):867-875). However, conditions for directing hESCs or iPSCs to differentiate along an alveolar epithelial lineage with high homogeneity have not yet been reported, and most protocols generate a mixed population of epithelial cells from hESCs or iPSCs.
Recently, the focus in organ engineering has centered on decellularizing complex organs such as heart, liver, and kidney, and using the acellular matrices as scaffolds for repopulation with organ-specific cells. Because the decellularized organ has the extracellular matrix template, it contains appropriate three-dimensional (3D) architecture and regionally-specific sites for cellular adhesion (Nichols J E, et al. 2012. J Cell Biochem 113(7):2185-2192, Petersen T H, et al. 2010. Science 329(5991):538-541). With extracellular matrix derived from donor lungs, the capacity to regenerate lung tissue from autologous cells (e.g., autologous iPS-derived epithelium) would therefore constitute a major medical advance. One way to accomplish this in lung engineering is to differentiate human iPSCs into respiratory epithelial cells and/or into putative postnatal stem cells of the respiratory system, and to reseed the lung acellular matrix with these cells (Badylak S F, et al. 2012. Lancet 379(9819):943-952).
There is a need in the art for regeneration of lung tissue from autologous cells. The present invention addresses this unmet need in the art.